Apparatus to control fluid flow rates

ABSTRACT

Apparatus for mixing two fluids has separate supply lines for delivering the fluids to a mixing head. Flow rate of fluid in one supply line is monitored by arranging a pressure transducer to measure a pressure drop across an orifice in an orifice plate arranged in the supply line and a controller is responsive to the detected flow rate to control flow rate of fluid in the other supply line to achieve a desired flow ratio of both fluids at the mixing head for producing a mixed fluid having the correct proportions of both fluids. The fluids may be a concentrate syrup and a plain or carbonated water to produce a beverage.

BACKGROUND OF THE INVENTION

This invention relates to an apparatus to control of the flow rates offluids. It is particularly concerned to provide a means whereby the flowrates of two or more fluids to be mixed are controlled and is especiallyintended for use in the mixing of the components of a post-mix beverage.

In the dispensing of a post-mix beverage, i.e. in which the componentsof the beverage are mixed at the point of sale from one or more fluidcomponents, e.g. a concentrated syrup and a diluent, usually plain orcarbonated water, it is obviously desirable to provide a mixed beverageof the correct ratio of components and it is important that this ratioshould not vary beyond tightly controlled limits. It is, therefore,desirable to have some means of determining the amount of each componentbeing provided to, for example, a dispense nozzle. One way of achievingthis is to determine the flow rate of each component, either by directmeasurement or by calculation after measurement of another property, andto calculate the amount dispensed from a series of flow ratedeterminations with respect to elapsed time.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an improved means ofaccurately mixing fluids, particularly beverage fluid components, in adesired ratio. It is also an objet of the present invention to providean improved means of determining fluid flow rate values.

Accordingly the invention herein provides an apparatus for the mixing ofat least two fluids, which comprises a first fluid supply lineconnectable to a source of the first fluid, a second fluid supply lineconnectable to a source of the second fluid. The invention also includesa mixing head into which the two fluids can be supplied through theirrespective supply lines and mixed therein and dispensed there from. Thefirst fluid supply line passes through an orifice in an orifice plateand a pressure transducer is positioned to measure the pressure drop inthe fluid passing through the plate. The pressure transducer providesthe measured pressure data to a controller, the controller beingpre-programmed with flow rate values determined over a range of pressuredrops for the first fluid and to control the rate of flow of the secondfluid to the mixing head in response to the flow rate of the first fluidto achieve a desired flow ratio of the two fluids. The controller mayallow flow for a predetermined time dependent on the monitored flowrates in order to achieve a specific volume of dispensed fluids.

As indicated above, the invention is particularly intended for use inthe dispensing of post-mix beverages and will, therefore, be moreparticularly described below with particular reference to thatembodiment. The mixing head may conveniently include a dispense nozzlefrom which the mixed beverage maybe dispensed into a suitablereceptacle. The first fluid is preferably a concentrated syrup and thesecond fluid is preferably a diluent, e.g. plain or carbonated water.The second fluid supply line may contain any suitable flow ratemeasuring device e.g. a flow turbine, and this is flow rate sensor isalso connected to the controller. Thus, the flow rate of the secondfluid/diluent may also be monitored in addition to the pressuretransducer monitoring of the first fluid/syrup. The controller is alsoconnected to a valve in the second fluid supply line and can cause thatvalve to be opened to the desired amount to achieve the required flowrate for the dispense ratio for the particular beverage being dispensed.

By monitoring the second fluid rate in conjunction with that of thefirst fluid rate and, where necessary, adjusting the second fluid flowrate to correspond to any variations in the monitored first fluid flowrate, the ratio of the dispensed beverage can be accurately maintainedat the required value. Thus any variations in the flow rate of theconcentrate of a post-mix beverage, e.g. due to pressure variations inthe supply line or delays in response of the on/off valve through whichthe concentrate is supplied, can be monitored and taken into account byrapid consequential adjustments to the diluent flow rate.

The concentrate supply line may contain a simple on/off valve to allowthe concentrate to flow when a beverage dispense is signalled to thecontroller. The controller then causes the valve, e.g. a solenoid ordiaphragm valve, to open while at the same time, or fractionallyearlier, opening the on/off valve in the diluent supply line andcommencing monitoring of the two flow rates. In this embodiment,therefore, the concentrate valve is either open or closed and when openit remains fully open to provide a particular nominal flow rate. Thevalve may have, e.g., a manual adjuster to fine tune this nominal flowrate for particular concentrates. The pressure transducer in thisembodiment is essentially, therefore, providing monitoring of flow ratefluctuations above and below the nominal rate through the fully openedvalve.

In another embodiment, the on/off valve in the concentrate flow line maybe controllable to provide a range of flow rates of the concentratewhereby the controller maybe programmed to control dispense of a widerrange of beverages based on a greater number of different concentratesthat may be supplied one at a time through the first fluid supply line.In a particular preferred version of this latter embodiment, the valvein the concentrate supply line is of the type described and claimed inour international patent publication WO99/29619 (application no.PCT/GB98/03564). That international application describes and claims avalve comprising a substantially rigid housing containing a passagewaybetween an inlet and an outlet of the valve, a closure member movable inthe passageway from a first position in which the valve is fully closedto a second position in which the valve is fully open, the closuremember engaging the wall of the passageway to seal the passageway, thewall of the passageway or the closure member defining at least onegroove, the groove having a transverse cross-section that increases inarea in the downstream or upstream direction, whereby movement of theclosure member from the first position towards the second position opensa flow channel through the groove. The groove(s) may be, for example, oftapering V-shape and will, for convenience, hereafter be referred to as“V-grooves” and the valves of this general type as “V-groove valves”,although it will be appreciated that the grooves may, if desired, have adifferent tapering cross-section, e.g. of circular, rectangular or othershape.

The progressive increase or decrease in area of the groove flow channelscan produce excellent linear flow through these V-groove valves, i.e.for a given pressure the flow rate is more directly proportional to thevalve position than for conventional valves. This enables better controlof the flow rate over the entire operating range of the valve.Alternatively the V-groove valve may be replaced, for example, by asolenoid, on/off valve upstream of a needle valve to provide the desiredrange of concentrate flow rates. The means to open and close theadjustable concentrate valve may be any suitable mechanism. A steppermotor or a linear solenoid actuator are amongst the preferredmechanisms.

The valve to control the flow of diluent may also be, if desired, aV-groove valve. Pressure transducers are well known in the art and theskilled man will readily be able to choose one suitable for hisparticular needs. Essentially, the pressure transducer measures fluidpressure at a particular point or surface and converts this measurementinto an electrical signal. The electrical signal is fed to the controlmeans which, therefore, is programmed to receive the pressure data inthis electrical form.

The orifice plate may be positioned upstream or downstream of the on/offvalve in the concentrate supply line but it is preferred that it beupstream as this arrangement, although possibly subject to staticpressure variations, is less Lady to be affected by variations in flowcharacteristics through the orifice plate. Nevertheless, it may bedesirable in certain circumstances to position the orifice platedownstream of the on/off valve and, in one such embodiment, the orificeplate may be positioned immediately before the outlet of the concentratesupply line to the mixing head. In this arrangement the plate can ventto atmosphere and the pressure transducer measures the pressureimmediately upstream of the plate. However, it is preferred to measurethe pressure difference across the orifice in the plate and this may bedone whether the plate is positioned upstream or downstream of theon/off valve. Preferably, the positioning of the orifice plate, when notventing to a atmosphere as described above, in the supply line should besuch that the supply line at the downstream side of the plate remainsfull of the concentrate. Thus the flow line through the plate shouldpreferably be uphill or at least horizontal. By this means there is lesslikelihood of trapped air affecting the pressure measurements and hencethe flow rate values.

It will be appreciated that fluid flow characteristics through theorifice plate are affected inter alia by the size of the orifice, thesharpness of the edge leading into the orifice and the thickness of theplate. In principle, the thinner the plate the better in that the fluidcan then effectively be considered to be passing through a very shorttube. The shorter the tube the less “re-attachment” effect of the fluidto the wall of the tube and the less undesirable effect on the flow andthe flow rate measurement. Clearly too thin a plate may buckle under thefluid pressure and we have, therefore, found, that as an alternative toa very sharp orifice edge on a slightly thicker plate, which edge maybeexpensive to manufacture, a chamfered edge leading into or leading outof the orifice may be usefully employed to give a predictablecharacteristic at the cost of slight increase in viscosity sensitivity.

Where the concentrate valve is adjustable to provide a range ofconcentrate flow rates, the controller may be programmed to provide a“profiled” dispense for the beverage. In other words, the initialportion of the dispense may, for example, be at a low flow rate, e.g. toprevent initial over-foaming of a carbonate beverage, and then the ratemay be increased to fall for the majority of the dispense period andthen reduced to a slower rate again for the final filling of the glassor other receptacle. Thus the dispense pour may be controlled to suitthe particular beverage in question.

As indicated above, the controller may be programmed to dispense anumber of different beverages. It may also be programmed to dispensedifferent volumes, e.g. a small portion and a large portion, of eachbeverage. The controller may also be programmed to take into accountviscosity changes due to temperature variations. This can be achieved bythe appropriate positioning of a temperature sensor in one or each fluidsupply lines so that the correct ratios of fluids can be maintainedregardless of temperature variations.

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the structure, function, objects andadvantages of the of the present invention can be had by reference tothe following detailed description with reference to the accompanyingdrawings, wherein:

FIG. 1 is a diagrammatic, representation of one apparatus of theinvention;

FIG. 2 is a part sectional view through a first orifice plate andpressure transducer arrangement for use in the invention;

FIG. 3 is a sectional view of second orifice plate and pressuretransducer arrangement for use in the invention;

FIG. 4 is a sectional view of a third orifice plate and pressuretransducer arrangement for use in the invention; and

FIG. 5 is an enlarged sectional view of an orifice plate for use in theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As seen in FIG. 1, an apparatus or system for dispensing a post-mixbeverage from a mixing/dispense head 10 is shown. A The apparatusincludes a dispensing valve having a dispensing valve body and aconcentrate flow line A from a source of concentrate (not shown) isindicted by single-headed arrows. A diluent, e.g. carbonated water, flowline B, again from a source not shown, is indicated by double-headedarrows. Concentrate flow line A passes through the orifice 12 of anorifice plate 14 and the pressure drop across the plate is measured bypressure transducer 16. Between the orifice plate and the mixing head 10is a variable on/off V-groove valve 18. Valve 18 has a throughpassageway 20 and a pair of opposed V-grooves 22 across the passageway,the cross-section of the grooves narrowing in the direction of flow offlow line A.

A piston 24 controlled by an actuator (not shown) completely closespassageway 20 in its fully lowered position by mating with internalwalls 26 beyond the narrow end of grooves 22. As the piston is movedupwards, the valve 18 opens and the through flow of concentrateincreases with increasing V-groove cross section until the fully openposition illustrated is reached. Diluent flow line B passes through aregulating valve 28 and a flow turbine 30 to reach mixing head 10. Acontroller 32, such as a microcontroller, receives signals from thepressure transducer 16 and from flow turbine 30. It is also connected toa control panel 34 via which a range of mixed beverages may becommanded. On receiving a command for a particular beverage, controller32 opens valve 28 to allow flow of diluent and simultaneously, ormarginally later, opens valve 18 by raising piston 24 to an appropriatedegree. By monitoring the flow rate of concentrate through line A andadjusting the flow rate through line B accordingly, the controllerensures that the desired ratio of fluids for the commanded beverage ismaintained. It may close the valves after a predetermined time or volumehas been dispensed.

In FIG. 2, there is shown one orifice plate/pressure transducerarrangement for the concentrate flow line. Direction of fluid flow isindicated by the arrows. An orifice plate 40 having a central orifice 42is positioned across the flow line passage 44 immediately above anoutlet nozzle 46 whereby the plate 40 vents to atmosphere. Hence theorifice plate here will be positioned downstream of the on/off valve forthe concentrate. A pressure transducer 48 measures the fluid pressureimmediately above plate 40 and by virtue of the venting to atmospherecan feed the pressure drop values across the plate to a suitablecontroller, such as controller 32 in FIG. 1.

In FIG. 3, an orifice plate 50 having a central orifice 52 is mouldedin-situ to lie across a portion 54 of second fluid flow line. A pressuretransducer 56 reads the fluid pressure values immediately upstream anddownstream of the plate 50 via stem tubes 58, 60 respectively. Stemtubes 58, 60 are a snap fit into orifices 62, 64 in the flow passagewayand are sealed into position by their respective O-rings 66, 68. Againthe pressure transducer feeds pressure data to a suitable controller, asdescribed above. The pressure transducer with the attachment stem tubesas shown in FIG. 3 is a well known attachment means but is notessential. An alternative arrangement is shown in FIG. 4. Here orificeplate 70 with central aperture 72 is again moulded in-situ to lie acrossa portion 74 of the second fluid flow line. Again pressure transducer 76reads the fluid pressure values immediately upstream and downstream ofplate 70 but directly via orifices 78, 80 i.e. without the stem tubes ofFIG. 3. Although flow through the orifice plates in FIGS. 3 and 4 isshown horizontal, as suggested above, it may be preferable for the flowto be uphill.

One suitable form of orifice plate 90 is shown in FIG. 5. It has acentral orifice 92, which has a chamfered edge 94 on one side of theplate. As indicated above, the chamfer may be on the upstream ordownstream side of the plate. By way of example only, the followingdimensions may be found to be suitable where the diluent to concentrateratio is 5 to 1 respectively and where the total flow rate of the twofluids is in the range of 1 and ½ to four ounces per second.

-   -   Plate thickness EE—about 1 mm.    -   Chamfer axial thickness DD—about 0.5 mm.    -   Orifice diameter CC—about 1.4 mm to 1.9 mm.    -   Chamfer angle x°=90°.    -   Pressure change at maximum concentrate flow rate between 10-30        p.s.i.

1. A dispensing valve system for mixing therein and dispensing therefrom a first fluid and a second fluid at a predefined ratio, comprising:a dispensing valve body having a first inlet and a second inlet forproviding connection to pressurized sources of the first fluid and thesecond fluid respectively, the first inlet delivering the first fluid toa first channel, the first channel having a pressure based flow sensingmeans, the second inlet delivering the second fluid to a second channeland the second channel having a second fluid flow sensing means thereinfor sensing the flow rate of the second fluid there through, and thesecond flow sensing means and the pressure based flow sensing meansconnected to a microcontroller for determining the flow rates of thesecond and first fluids respectively, a valve in the first channel andoperated by the microcontroller for regulating the flow of the firstfluid there thorough in an on/off manner, a linear actuator controlledby the microcontroller for operating a rod extending in the secondchannel, the rod having a rod end movable to a stop position forstopping the flow of the second fluid and to a full flow position forpermitting a maximum flow of the second liquid and movable to aplurality of positions between the stop and full open positions forregulating the flow rate of the second fluid as a function of the sizeof a flow orifice created between the rod and the second channelrelative to the position of the rod end between the stop and full flowpositions, and the microcontroller regulating the flow rate of thesecond fluid as a function of the sensed flow rate of the first fluid soas to maintain the predetermined ratio there between.
 2. The dispensingvalve system as defined in claim 1, and where the first fluid is a syrupconcentrate and the second fluid is a water diluent.
 3. The dispensingvalve system as defined in claim 1, and the pressure based flow sensingmeans including an orifice plate in the first channel and extendingtherein transverse to the flow of the first fluid there through and theorifice plate having two side surfaces and a central hole there throughand the central hole having a chamfered edge around a perimeter thereofformed into a portion of one of the side surfaces.
 4. The dispensingvalve system as defined in claim 2, and the pressure based flow sensingmeans including an orifice plate in the first channel and extendingtherein transverse to the flow of the first fluid there through and theorifice plate having two side surfaces and a central hole there throughand the central hole having a chamfered edge around a perimeter thereofformed into a portion of one of the side surfaces.
 5. An apparatus forproviding a mixture of at least two fluids, which comprises a firstfluid supply line connectable to a source of the first fluid, a secondfluid supply line connectable to a source of the second fluid, and amixing head into which the two fluids can be supplied through theirrespective supply lines and mixed therein, the first fluid supply lineincluding an orifice plate, the orifice plate having a chamfered edgeleading into its orifice in the direction of flow, and pressuretransducer means for measuring the pressure drop in the first fluid asit passes through the orifice plate, the pressure transducer meansproviding the measured pressure drop to a controller, the controllerbeing pre-programmed with flow rate values determined over a range ofpressure drops for the first fluid and to control the rate of flow ofthe second fluid to the mixing head in response to the flow rate of thefirst fluid to achieve a desired flow ratio of the two fluids, in whichthe first fluid supply line contains a multiple position on/off valvecontrollable to provide a range of flow rates of the first fluid, and inwhich the controllable on/off valve comprises a substantially rigidhousing containing a passageway between an inlet to and an outlet fromthe valve, a closure member movable in the passageway from a firstposition in which the valve is fully closed to a second position inwhich the valve is fully open, the closure member engaging the wall ofthe passageway to seal the passageway, at least one of the wall of thepassageway and the closure member defining at least one groove, thegroove having a transverse cross-section that increases in area in oneof the downstream and upstream directions, such that movement of theclosure member from the first position towards the second positionprogressively opens a flow channel through the groove.
 6. An apparatusaccording to claim 5, in which the at least one groove is of taperingV-shape.
 7. An apparatus for providing a mixture of at least two fluids,which apparatus comprises a first fluid supply line connectable to asource of the first fluid, a second fluid supply line connectable to asource of the second fluid, a mixing head into which the two fluids canbe supplied through their respective supply lines and mixed therein, andpressure based flow sensing means in which a pressure transducermeasures fluid pressure on one side of an orifice plate having anorifice while an opposite side of the orifice plate vents to atmosphere,said pressure based flow sensing means comprising an orifice in anorifice plate arranged to vent to atmosphere and through which orificethe first fluid supply line passes, a pressure transducer immediatelyupstream of the orifice plate to measure the pressure drop in the fluidpassing through the plate, the pressure transducer providing themeasured pressure drop to a controller that is pre-programmed with flowrate values determined over a range of pressure drops for the firstfluid and to control the rate of flow of the second fluid to the mixinghead in response to the flow rate of the first fluid to achieve adesired flow ratio of the two fluids, in which the first fluid supplyline contains a controllable on/off valve upstream of the orifice plateand pressure transducer, and in which the controllable on/off valvecomprises a substantially rigid housing containing a passageway betweenan inlet to and an outlet from the valve, a closure member movable inthe passageway from a first position in which the valve is fully closedto a second position in which the valve is fully open, the closuremember engaging the wall of the passageway to seal the passageway, atleast one of the wall of the passageway and the closure member definingat least one groove, the groove having a transverse cross-section thatincreases in area in one of the downstream and upstream directions,whereby movement of the closure member from the first position towardsthe second position opens a flow channel through the groove.
 8. Anapparatus according to claim 7, in which the grooves are of taperingV-shape.